1. Field of the Invention
The invention relates to the field of voltage converters employing CMOS devices.
2. Prior Art
Complementary metal-oxide-silicon (CMOS) devices have been utilized in applications where low power consumption is required, such as in electronic watches. In such watches and in other applications voltages higher than those economically available from batteries are required for displays, particularly for liquid crystal displays. In the prior art numerous circuits are known for raising a battery potential, for example, of 1.5 volts, to a higher potential such as 4.5 volts for activating displays.
Generally, the prior art voltage converting circuits employ resistors, diodes, inductors and bipolar transistors in a resonant transfer circuit. These components cannot be integrated into the CMOS circuit used for the remainder of the watch circuitry. Moreover, such components are relatively expensive when compared to the remainder of the watch electronics.
As will be seen, the present invention provides a voltage converter employing only CMOS active devices although external capacitors are utilized in the presently preferred embodiment. The presently disclosed circuit provides a less expensive, and more efficient, converter than known in the prior art.